I dont have a single stack 223 mag but Im guessing it would be to narrow. I put it in a doublestack plastic bulgy Mag and except for the lips not holding the roumd in place it seemed to fit ok. sectoining a G2 308 mag would work possably but would be a lot of work.

could name it the 444 GSRSM (Gunco Super SHORT Rimless MAGNUM) drived from a short 444 marlin rimlesss
or just the 44 GM
or the 44 BBSKMA ( Beowulf Bushmaster SOCOM Kiss My Ass )
or the 430-06S would allow adding a 4 to the exsiting head stamp the S stands for short would be able to make the factory head stamp look original.
THE 44??? is a cool name to excuse me while I whip out the ole 44 question mark!
the 444 TT (444 Triple Threat)
MY main concern would be the feeding and extraction of empty brass with very little taper. head spacing off the case mouth is also a issue.
the .41 and the .375 versions of this round should not be overlooked.
This round would work very well on 223 length bolt actions very well also and you can bet If I have to shell out for a reamer there will be a savage bolt action 44??? barrel for my 223 made.

Like you said the .375 might be better as there is a wider range of bullets. The .375 Shannon and .375/38-40 Rimless would be close. Plus it would have a shoulder to headspace off of. Not a big fan of headspacing off the mouth either.

Honestly the mag modification isn't really that hard! These would fit into a G3 mag with a little extra space. Right? Could you cut a mag short, leaving enough for tabs, then add a spine with holes that the tabs can fold in to.

Or you could do like VZ and I are doing and just buy some square tubing and use some AK mag springs.

It seems to fit the G3 mag very well just to long. I was thinking of just taking a section out in the middle doing some type of overlap and a couple tig welds. I have like a dozen from when tapco had them cheap. I had planed to mod one for my 444 marlin build as that round is shorter than a 308. this would free up some trigger guard space on that build. I think a 450 bush master or possabley a 458 socom AR mag might be workable but the cost and still having to mod it might not be worth it. the g3 would need a differant springng if it was modifed. I think a steel 223 mag with a lip mod would be the easiest not the cheapest though. I think a single stack would be the best as far as getting it to feed. I am starting to think a custom reamer might be worth the $$$$

Barrel twist will have a large factor as to what bullets this or any .44 based weapon can shoot. Is there a place you can buy taperd case expanders?? I am thinking of getting new 444 marlin dies likely RCBS so I can get bits and pieces to intechange of the same brand. that way if this round does come to fruitation It can be reloaded with currently avaliable dies and listed part numbers sort of a way to standardize it. I am sure if one could get final version built and a gun that functions correctly that custom reamers and die sets could be made that would be worth the money.

I am still thinking a .41 0r .375 version might be better. yea the .45 bushmaster,458 socom and .50 grendal are bigger but so what. they also have slower MV and kick like hell. How many people really want one other than the mines bigger than yours thing?? In reality with the limited powder capacity a .375 0r .41 or .416 bullet is going to likely have better performance and accuracy further out. the .375 has bullets up to around 300 grains and the 416 has bullets up to around 400 grain. (about he same as the .44). The the 325 grain bullet that the 416 rigby and the 416 weatherby use, would possably be a good choice for hunting. there is a 400 grain round nose solid for you guys that think you are going to go Rambo and need to shoot through solid doors and army tanks and all that. IMOA it is cool to say yea mines bigger than yours BUT how many guys actually hunt with a 460weatherby magnum??? there is a reason that 7mm to .35 cal rounds are the most popular in north america. unless I am going RINO hunting in Wisconsin soon I thing maybe a little smaller might be a lot better. If you want to give it a Macho name call it the 375 Anti SUBURBAN SUPRRESSION HOSTILE OVERLY LOUD ELEMINATOR. OR A.S.S.H.O.L.E for short. LOL